12 oz bittersweet (not unsweetened) or semisweet chocolate, chopped
¾ cup (1 ½ stick) unsalted butter, cut into pieces
6 large eggs separated
12 Tbs sugar
2 tsp vanilla extract
Whipped cream (if desired)
Preheat oven to 350o F. Butter 9-inch diameter springform pan. Line bottom of pan with parchment paper or waxed paper, butter paper.
Stir chocolate and butter in heavy medium saucepan over low heat until melted and smooth (can also microwave). Remove from heat. Cool to lukewarm, stirring often.
Using mixer, beat egg yolks and 6 Tbs sugar in large bowl until mixture is very thick and pale, about 3 minutes. Fold lukewarm chocolate mixture into yolk mixture, then fold in vanilla extract.
Beat egg whites in another large bowl until soft peaks form. Gradually add remaining 6 Tbs sugar, beating until medium-firm peaks form. Fold whites into chocolate mixture in 3 additions.
Pour batter into prepared pan. Bake until top is puffed and cracked and toothpick inserted into center comes out with some moist crumbs attached, about 50 minutes. Cool cake in pan on rack. Cake will collapse and this is okay!
Gently press down crusty top to make evenly thick cake. Using a small knife, cut around pan sides to loosen cake. Remove pan sides. Place 9-inch diameter tart pan bottom or cardboard round atop cake. Invert cake onto tart pan bottom. Peel off parchment paper.
Steven and I learned how to make this in a cooking class for a friend’s birthday party. You can serve it warm with whipped cream. It’s also a good option for a Passover dessert.